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THE NATIONAL GEOGRAPHIC MAGAZINE
EXCAVATIONS MADE IN SEARCHING FOR HIBERNATING SQUIRRELS
At first, for fear that they were missing the squirrels, the investigators carefully followed
every burrow. Later, before beginning the work of careful excavation, deep trenches were
dug down to subsoil completely around the main body of the den for fear the squirrels might
awaken and escape through some radiating burrow. A fairly large den may cover a radiating
area of 30 by 40 feet.
From the knife at
THE VERTICAL SECTION OF A HIBERNATING DEN
the left is. first, the exposed nest; next, the round hole leading upward for
the spring exit; and then the drain leading downward.